BO with runny poop and dirty butt

I have a flock of 6 hens (all kinds) and one roo. They're very healthy, active, and laying 5-6 eggs a day. My BO hen, Sarah, has had a dirty behind for about a week or so. She is VERY plump, and at first I thought that could be the problem, but this morning I noticed dark brown, runny poop all around her vent. She's eating normal (she's the greediest of all my chickens), and seems to be laying. No "sick" behaviour, other than the runny poop on her behind. I give all of them jogurt every day, and their water has ACV in it.
What do to?

SEVEN FEATHERS FARM: 3 dogs, 2 cats, 3 goats, 2 ducks, 16 chickens and 1 fish. "But for the sake of some little mouthful of flesh, we deprive a soul of sun and light, and of that proportion of life and time it had been born into the world to enjoy!" (Plutarch)

SEVEN FEATHERS FARM: 3 dogs, 2 cats, 3 goats, 2 ducks, 16 chickens and 1 fish. "But for the sake of some little mouthful of flesh, we deprive a soul of sun and light, and of that proportion of life and time it had been born into the world to enjoy!" (Plutarch)

OK, The straight skinny on "Pasty Butt". Believe it or not, Pasty Butt is a symptom of constipation. The cure is molasses in their drinking water. Molasses is a natural laxative for fowl. Mix it like weak tea and give it to them for 2 days. Naturally you should clean their little butts with a warm damp cloth before you start the treatment. Failure to cure this condition could result in a painful death for your chicken. This treatment is for adult birds as well as chicks.

In God We Trust

Siyah Rampuri Asil, White Chinese, Emden, and African Geese, Guineas, a Rottweiler (Bella), and a Yellow Lab (Booger). Fifty five years with chickens and still learning.

OK, The straight skinny on "Pasty Butt". Believe it or not, Pasty Butt is a symptom of constipation. The cure is molasses in their drinking water. Molasses is a natural laxative for fowl. Mix it like weak tea and give it to them for 2 days. Naturally you should clean their little butts with a warm damp cloth before you start the treatment. Failure to cure this condition could result in a painful death for your chicken. This treatment is for adult birds as well as chicks.

Great, that sounds like a pretty easy fix! Should I separate her from the others, or can they all take a little dose of "chicken laxative"?

SEVEN FEATHERS FARM: 3 dogs, 2 cats, 3 goats, 2 ducks, 16 chickens and 1 fish. "But for the sake of some little mouthful of flesh, we deprive a soul of sun and light, and of that proportion of life and time it had been born into the world to enjoy!" (Plutarch)

SEVEN FEATHERS FARM: 3 dogs, 2 cats, 3 goats, 2 ducks, 16 chickens and 1 fish. "But for the sake of some little mouthful of flesh, we deprive a soul of sun and light, and of that proportion of life and time it had been born into the world to enjoy!" (Plutarch)